The accuracy and validity of a document scanning system requires reliable monitoring of the movement of the document through the transport system which is responsible for moving the document through the optical scanning apparatus. The tracking of the document through the transport of an optical scanning system has typically been accomplished through the use of optical sensors positioned along the transport path in conjunction with a set of timers that function to detect a document jam. This technique is complicated inasmuch as each timer must be adjusted individually, and any change in the transport speed, i.e., the speed of the movement of the document through the system, requires a complete readjustment of all the timers.